Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS For disclosure purposes, qualifying assets and liabilities are categorized into three broad levels based on the priority of the inputs used to determine their fair values. The fair value hierarchy gives the highest priority to quoted prices (unadjusted) in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). Certain assumptions and other information as they relate to these qualifying assets and liabilities are described below. Goodwill and Other Intangible Assets As discussed in Note 7, Quanta has recorded goodwill and identifiable intangible assets in connection with certain of its historical business acquisitions. Quanta utilizes the fair value premise as the primary basis for its impairment valuation procedures. The Goodwill and Other Intangible Assets sections within Notes 2 and 7 provide information regarding valuation methods, including the income approach, market approach and cost approach, and assumptions used to determine the fair value of these assets based on the appropriateness of each method in relation to the type of asset being valued. Quanta believes that the valuation methods it employs appropriately represent the methods that would be used by other market participants in determining fair value, and periodically engages the services of an independent valuation firm when a new business is acquired to assist management with the valuation process, including assistance with the selection of appropriate valuation methodologies and the development of market-based valuation assumptions. The level of inputs used for these fair value measurements is the lowest level (Level 3). Investments Equity investments with readily determinable fair values are measured at fair value, with changes in fair value recognized in net income. In cases where those readily determinable values are quoted market prices, the level of input used for fair value measurements is the highest level (Level 1). Equity investments without readily determinable fair values are measured on a nonrecurring basis. These types of fair market value assessments are similar to other nonrecurring fair value measures used by Quanta, which include the use of significant judgments and available relevant market data. Such market data may include observations of the valuation of comparable companies, risk-adjusted discount rates and an evaluation of the expected performance of the underlying portfolio asset, including historical and projected levels of profitability or cash flows. In addition, a variety of additional factors may be reviewed by management, including, but not limited to, contemporaneous financing and sales transactions with third parties, changes in market outlook and the third-party financing environment. The level of inputs used for these fair value measurements is the lowest level (Level 3). Quanta has investments accounted for using the equity and cost methods of accounting as discussed in Note 8. Quanta utilizes the fair value premise as the basis for its impairment valuation and recognizes impairment if there are sufficient indicators that the fair value of the investment is less than its carrying value. Quanta also has COLI policies related to its deferred compensation plan as further described in Note 15. These policies are carried at their cash surrender value, which is considered their fair value. The level of input used for these fair value measurements is Level 2. Financial Instruments The carrying amounts of cash equivalents, accounts receivable, contract assets, accounts payable, accrued expenses and contract liabilities approximate fair value due to the short-term nature of these instruments. All of Quanta’s cash equivalents were categorized as Level 1 assets at December 31, 2021 and 2020, as all values were based on unadjusted quoted prices for identical assets in an active market that Quanta has the ability to access. Contingent Consideration Liabilities Financial instruments required to be measured at fair value on a recurring basis consist primarily of Quanta’s liabilities related to contingent consideration associated with certain acquisitions, payable in the event certain performance objectives are achieved by the acquired businesses during designated post-acquisition periods. The liabilities recorded represent the estimated fair values of future amounts payable to the former owners of the acquired businesses and are estimated by management based on entity-specific assumptions that are evaluated on an ongoing basis. The fair values of these liabilities described in Note 6 were primarily determined using a Monte Carlo simulation valuation methodology based on probability-weighted performance projections and other inputs, including a discount rate and an expected volatility factor for each acquisition. The expected volatility factor was 50.0% based on historical asset volatility of selected guideline public companies. Depending on contingent consideration payment terms, the present values of the estimated payments are discounted based on a risk-free rate and/or Quanta’s cost of debt and ranged from 0.04% to 3.9% and had a weighted average of 1.9% based on the fair value at the dates of the respective acquisitions. The fair value determinations incorporate significant inputs not observable in the market. Accordingly, the level of inputs used for these fair value measurements is the lowest level (Level 3). Significant changes in any of these assumptions could result in a significantly higher or lower potential liability. Long-Term Debt The carrying amount of variable rate debt, which includes borrowings under Quanta’s senior credit facility, approximates fair value. Quanta’s fixed rate debt primarily includes its Senior Notes. The fair value of Quanta’s Senior Notes, which are described further in Note 10, was $2.49 billion at December 31, 2021, compared to a carrying value of $2.47 billion net of unamortized bond discount, underwriting discounts and deferred financing costs of $27.0 million. The fair value of the senior notes is based on the quoted market prices for the same issue and are categorized as Level 1 liabilities. See Note 10 for additional information regarding Quanta’s senior credit facility and the Senior Notes.

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.